楔形工字梁抗剪极限承载力试验研究

该文介绍了楔形变截面工字钢短梁的抗剪承载力试验,与有限元结果进行了对比,提出了将楔形变截面梁的承载力按等截面梁的承载力乘以楔率折减系数的计算方法,与试验和扩充的有限元计算结果对比表明:公式有很好的精度.     

考虑板件相关作用的H形截面压弯钢构件抗弯承载力

对H形截面钢构件绕强轴压弯的极限抗弯性能展开研究。基于经实验校准的非线性有限元模型,进行了不同翼缘宽厚比、腹板宽厚比及轴压比组配下的H形截面钢构件的单调压弯全过程的参数分析,并对破坏模式进行了机理分析。研究表明,翼缘与腹板存在明显的相关作用,而板件屈曲形式决定了极限状态的应力分布形式,因此计算极限承载力时应考虑板件相关作用。以极限状态的应力分布特点为基础,提出了考虑板件塑性阶段屈曲相关作用的有效塑性宽度法计算截面的极限抗弯承载力。经与实验及有限元极限承载力的比较,显示该方法能够准确预测H形截面压弯构件的极限承载力。     

冲击载荷作用下夹芯板的后屈曲研究

利用ABAQUS有限元软件,对SHPB作用下的夹芯板的变形特性进行了分析,将有限元计算结果和实验测量结果作对比。在冲击载荷时间历程内,着重从芯板的位移和应力以及应变这3个方面对芯板的后屈曲问题进行了分析,研究了夹芯板中弹塑性压缩波的传播过程,芯板在压缩波作用下的动力屈曲产生、传播特性,压缩波与屈曲变形的相互作用以及塑性后屈曲大变形的发展规律。     

Problems of structural optimization for post-buckling behaviour

A proposal of a new approach to the optimal design of structures under stability constraints is presented. It is shown that the standard problem of maximization of the instability load may be modified so as to obtain a specified post-critical behaviour of the designed structure. The modified optimal structure represents stable post-buckling behaviour either locally, that is, in the vicinity of the critical point, or for a specified range of generalized displacements. First, some rigid–elastic finite-degree-of-freedom models are optimized, giving an insight into the modified design problems. Then a classification of the new optimization problems is presented. Various forms of instability are taken into account and a broad selection of objective as well as constraint functions is proposed. Based on the presented classification and following the proposed optimization concept, detailed formulations of nonlinear problems of design for post-buckling behaviour are given.     

POST-BUCKLING ANALYSIS WITH FRICTIONAL CONTACTS COMBINING COMPLEMENTARITY RELATIONS AND AN ARC-LENGTH METHOD

A linear complementarity problem formulation combined with an arc-length method is presented for post-buckling analysis of geometrically non-linear structures with frictional contact constraints. The arc-length method with updated normal plane constraint is used to trace the equilibrium paths of the structures after limit points. Under the proportional loading assumption, the unknown load scale parameter used in the arc-length method is expressed in terms of contact forces, and eliminated to formulate as a linear complementarity problem. The unknown contact variables such as contact status and contact forces can be directly solved in this formulation without any ad hoc technique. Complicated non-linear buckling behaviours, such as snap-buckling, can be efficiently solved by the developed method, as shown by several buckling and post-buckling problems with frictional contact constraints.     

复合材料加筋板屈曲/后屈曲分析的应用

研究了复合材料加筋板翼面结构稳定性问题,分析了加筋板在压缩和剪切等载荷作用下的稳定性安全裕度。利用计算复合材料加筋板屈曲及后屈曲承载能力的方法,验证复杂受载情况下结构的稳定性。验证对象是一个优化后的满足强度、刚度和工艺制造要求的复合材料机翼。该机翼在各种载荷工况下的内力分布情况由MSC.NASTRAN分析得到,通过本文提出的方法得到每块蒙皮的稳定性承载能力。然后给出复合材料层合板在复杂载荷下的屈曲及后屈曲安全裕度的计算准则,验证优化后的机翼加筋板是否满足稳定性设计要求。该方法可作为约束集成到结构优化系统平台中。     

双向增强体复合地基桩土应力比计算

针对竖向增强体-水平增强体-桩间土的整体相互作用特点,将水平向加筋垫层视为具有一定刚度的板,竖向桩体及桩间土简化为刚度不同的弹簧系列。以单个竖向桩体影响范围内的复合地基作为典型单元体进行分析,基于Winkler弹性地基圆板理论推导出水平加筋体的挠曲函数表达式,导出双向增强体复合地基桩土应力比计算式。最后对某工程算例进行计算分析,对路堤荷载大小、工后沉降值、面积置换率、桩土刚度比进行了参数研究,并探讨了桩土应力比随其主要影响因素的变化规律,计算与实测结果吻合较好。     

Nonlinear thermomechanical post-buckling of circular FGM plate with geometric imperfection

Nonlinear thermomechanical post-buckling of an imperfect functionally graded material (FGM) circular plate, subjected to both mechanical load and transversely non-uniform temperature rise, is presented. The material properties of FGM plates are assumed to be graded in the thickness direction according to a simple power law distribution in terms of the volume fractions of the constituents. Based on von Kármán's plate theory, equilibrium equations governing a large axi-symmetric deformation of the FGM circular plate under thermomechanical loads are derived. In the analysis, the geometric imperfections of the plate are taken into account. By using a shooting method the nonlinear ordinary differential equations with immovably clamped boundary conditions are solved numerically. Responses for the nonlinear thermomechanical post-buckling responses of the FGM plate are obtained. Numerical examples are presented that relate to the performances of perfect and imperfect, homogenous and graded plates. Characteristic curves of the post-buckling deformation of the imperfect FGM circular plate varying with thermal loads, imperfection parameters and volume fraction index are plotted. And then effects of the load parameters, materials constitution, and the geometric imperfection of the plate on the deformation are discussed in detail.     

中国现行钢结构规范(规程)与美国ASD规范的主要限值

通过比较现行中、美两国的钢结构设计规范、规程中对受压杆件的长细比、翼缘宽厚比、腹板高厚比的极限值规定,阐述两国规范、规程中的差异和近似之处。